Effect of a Residual Stenosis by Quantitative Angiography on the Myocardial Contrast Defect Observed Following Coronary Reperfusion Using Intermittent Harmonic Ultrasound Imaging and Intravenous Perfluorocarbon Ultrasound Contrast.

ABSTRACT

Intermittent harmonic imaging following intravenously injected perfluorocarbon-containing microbubbles can detect myocardial perfusion abnormalities caused by ischemia. It is unknown whether this technique can differentiate viable, ischemic myocardium from infarcted myocardium immediately following coronary reperfusion. The objective of this paper was to determine whether intermittent harmonic imaging with intravenous microbubbles could define myocardial perfusion abnormalities following reperfusion. In 26 dogs, a prolonged total coronary occlusion (mean occlusion time 2.1 +/- 0.4 hours) was followed by coronary reperfusion. Wall thickening (WT) and peak myocardial video intensity (PMVI) within and outside the risk area (PMVI ratio) were measured following intravenous perfluorocarbon microbubbles under resting conditions and during a 5 µg/kg per minute dobutamine [low dose dobutamine (LDD)] infusion in the presence and absence of a >/= 50% diameter stenosis in the reperfused vessel. Infarct size was determined postmortem. The resting contrast defect in all dogs correlated closely (r = 0.93) with infarct size when no residual stenosis was present but correlated more closely with risk area (r = 0.88) when a >/= 50% diameter residual stenosis was present. In dogs with infarction involving > 50% of the risk area, the PMVI ratio was lower under resting conditions (0.51 +/- 0.27) than in dogs with no or partial infarction when no residual stenosis was present. However, in dogs with no or partial infarction, the PMVI ratio fell significantly when a >/= 50% diameter stenosis was present, both under resting conditions and during LDD. We conclude that the myocardial contrast defect observed with intermittent harmonic imaging and intravenous ultrasound contrast is affected by both the infarct size and the presence of a significant residual stenosis.